| Message ID | 1a3890966d68b9f800d457cbf095746627495e18.camel@iris-sensing.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] pwm: imx-tpm: Use correct MODULO value for EPWM mode | expand |
Hello, On Fri, Oct 25, 2024 at 08:37:00AM +0000, Erik Schumacher wrote: > The modulo register defines the period of the edge-aligned PWM mode > (which is the only mode implemented). The reference manual states: > "The EPWM period is determined by (MOD + 0001h) ..." So the value that > is written to the MOD register must therefore be one less than the > calculated period length. Return -EINVAL if the calculated length is > already zero. > A correct MODULO value is particularly relevant if the PWM has to output > a high frequency due to a low period value. > > Fixes: 738a1cfec2ed ("pwm: Add i.MX TPM PWM driver support") > Cc: stable@vger.kernel.org > Signed-off-by: Erik Schumacher <erik.schumacher@iris-sensing.com> Applied to https://git.kernel.org/pub/scm/linux/kernel/git/ukleinek/linux.git pwm/fixes I let it sit there for a few days to get some coverage in next and then intend to send it to Linus for mainline inclusion ~ mid of next week. Best regards Uwe
diff --git a/drivers/pwm/pwm-imx-tpm.c b/drivers/pwm/pwm-imx-tpm.c index 96ea343856f0..7ee7b65b9b90 100644 --- a/drivers/pwm/pwm-imx-tpm.c +++ b/drivers/pwm/pwm-imx-tpm.c @@ -106,7 +106,9 @@ static int pwm_imx_tpm_round_state(struct pwm_chip *chip, p->prescale = prescale; period_count = (clock_unit + ((1 << prescale) >> 1)) >> prescale; - p->mod = period_count; + if (period_count == 0) + return -EINVAL; + p->mod = period_count - 1; /* calculate real period HW can support */ tmp = (u64)period_count << prescale;
The modulo register defines the period of the edge-aligned PWM mode (which is the only mode implemented). The reference manual states: "The EPWM period is determined by (MOD + 0001h) ..." So the value that is written to the MOD register must therefore be one less than the calculated period length. Return -EINVAL if the calculated length is already zero. A correct MODULO value is particularly relevant if the PWM has to output a high frequency due to a low period value. Fixes: 738a1cfec2ed ("pwm: Add i.MX TPM PWM driver support") Cc: stable@vger.kernel.org Signed-off-by: Erik Schumacher <erik.schumacher@iris-sensing.com> --- v2: - Add Fixes: and Cc: tags v3: - Add period_count == 0 check and return -EINVAL drivers/pwm/pwm-imx-tpm.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)